Abstract:

An over-current protection device for multiple high-voltage motive devices
is provided. The over-current protection device includes a comparison
module and a logic operation module. The comparison module receives a
plurality of voltages generated from a plurality of operating currents of
a plurality of high-voltage motive devices and respectively compares the
voltages with at least one reference voltage to generate a plurality of
comparison results, wherein the high-voltage motive devices are
solenoids, electronic clutches, or a combination of solenoids and
electronic clutches. The logic operation module receives the comparison
results and generates at least one control signal for a plurality of
high-voltage motive device driving circuits according to the comparison
results. The high-voltage motive device driving circuits respectively
drive the high-voltage motive devices according to the control signal.

Claims:

1. An over-current protection device for multiple high-voltage motive
devices, comprising:a comparison module, for receiving a plurality of
voltages generated from a plurality of operating currents of a plurality
of high-voltage motive devices and respectively comparing the voltages
with at least one reference voltage to generate a plurality of comparison
results, wherein the high-voltage motive devices are a plurality of
solenoids, a plurality of electronic clutches, or a combination of the
solenoids and the electronic clutches; anda logic operation module, for
receiving the comparison results and generating at least one control
signal for a plurality of high-voltage motive device driving circuits
according to the comparison results, wherein the high-voltage motive
device driving circuits respectively drives the high-voltage motive
devices according to the control signal.

2. The over-current protection device according to claim 1 further
comprising a main power control module, wherein the logic operation
module further generates a main power control signal for the main power
control module according to the comparison results, and the main power
control module generates a main power off control signal for a main power
circuit according to the main power control signal so that the main power
circuit turns off a high-voltage motive device voltage source supplied by
the main power circuit according to the main power off control signal.

3. The over-current protection device according to claim 2, wherein the
main power control module comprises:an integrator, for receiving the main
power control signal and generating an integrated voltage accordingly;
anda comparator, for receiving a predetermined voltage and the integrated
voltage and comparing the integrated voltage with the predetermined
voltage to generate the main power off control signal.

4. The over-current protection device according to claim 2 further
comprising a processor, wherein the logic operation module generates at
least one power-off indication signal according to the comparison
results, the processor outputs at least one prompt signal to the logic
operation module according to the power-off indication signal, and the
logic operation module generates the control signal according to the
power-off indication signal and the prompt signal.

5. The over-current protection device according to claim 4 further
comprising a display module, wherein the processor generates an warning
signal according to the power-off indication signal, and the display
module receives the warning signal and displays error states of the
high-voltage motive devices according to the warning signal.

6. The over-current protection device according to claim 2, wherein when
the voltage generated from the operating current of one of the
high-voltage motive devices is greater than the reference voltage, the
logic operation module outputs the control signal to turn off one, all,
or a part of the high-voltage motive devices, or the main power control
module turns off the high-voltage motive device voltage source supplied
by the main power circuit.

7. The over-current protection device according to claim 1, wherein the
logic operation module comprises at least one logic gate.

8. The over-current protection device according to claim 1, wherein the
comparison module comprises a plurality of comparators, and the
comparators respectively compare the voltages with the reference voltage
and generate the comparison results.

9. The over-current protection device according to claim 1, wherein one of
the voltages is generated by a current detector through detection of the
corresponding operating current.

10. The over-current protection device according to claim 1, wherein the
reference voltage is generated by a reference voltage generator.

11. An over-current protection method for multiple high-voltage motive
devices, comprising:receiving a plurality of voltages generated from a
plurality of operating currents of a plurality of high-voltage motive
devices, wherein the high-voltage motive devices are a plurality of
solenoids, a plurality of electronic clutches, or a combination of the
solenoids and the electronic clutches;respectively comparing the voltages
with at least one reference voltage to generate a plurality of comparison
results;performing at least one logic operation on the comparison results
to generate at least one control signal for a plurality of high-voltage
motive device driving circuits; andrespectively driving the high-voltage
motive devices according to the control signal by using the high-voltage
motive device driving circuits.

12. The over-current protection method according to claim 11 further
comprising:performing the logic operation on the comparison results to
generate a main power control signal for a main power control module;
andgenerating a main power off control signal for a main power circuit
according to the main power control signal by using the main power
control module, so that the main power circuit turns off a high-voltage
motive device voltage source supplied by the main power circuit according
to the main power off control signal.

13. The over-current protection method according to claim 12, wherein the
step of generating the main power off control signal
comprises:integrating the main power control signal to generate an
integrated voltage; andcomparing the integrated voltage with the
predetermined voltage to generate the main power off control signal.

14. The over-current protection method according to claim 12, wherein the
step of generating the control signal comprises:performing the logic
operation on the comparison results to generate at least one power-off
indication signal for a processor;generating at least one prompt signal
according to the power-off indication signal; andperforming the logic
operation on the power-off indication signal and the prompt signal to
generate the control signal.

15. The over-current protection method according to claim 14 further
comprising:performing the logic operation on the comparison results to
generate a warning signal; anddisplaying error states of the high-voltage
motive devices according to the warning signal.

16. The over-current protection method according to claim 12, wherein when
the voltage generated from the operating current of one of the
high-voltage motive devices is greater than the reference voltage, the
control signal is used for turning off one, all, or a part of the
high-voltage motive devices, or the main power control module turns off
the high-voltage motive device voltage source supplied by the main power
circuit.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001]This is a continuation-in-part application of patent application
Ser. No. 12/216,657 filed on Jul. 9, 2008, which claims the priority
benefit of Taiwan patent application serial no. 97116753, filed May 7,
2008 and is now pending. This application also claims the priority
benefits of Taiwan application serial no. 99125605, filed on Aug. 2,
2010. The entirety of each of the above-mentioned patent applications is
hereby incorporated by reference herein and made a part of this
specification.

BACKGROUND OF THE INVENTION

[0002]1. Field of the Invention

[0003]The present invention generally relates to a printing device, and
more particularly, to an over-current protection device for multiple
high-voltage motive devices and a method thereof, wherein the
high-voltage motive devices in a printing device are protected at the
same time.

[0004]2. Description of Related Art

[0005]A plurality of high-voltage motive devices is usually disposed in a
multifunction printer (MFP) for converting electric power into mechanical
power such that the printing operations can be successfully carried out.
The high-voltage motive devices may be solenoids or electronic clutches.
However, when a MFP fails or an instantaneous mis-operation occurs (for
example, a paper jam causes various elements to stop working), the
high-voltage motive devices and the power supply circuit thereof may
continue to receive a high voltage or current and accordingly be damaged.
In a worst-case scenario, the damage of the high-voltage motive devices
may be spread to other elements and even cause the entire MFP to get
burnt.

[0006]Conventionally, sheet metals are installed on the high-voltage
motive devices of a MFP to prevent the damage of the high-voltage motive
devices from spreading to other elements. However, the fabrication cost
of the MFP is increased by installing the sheet metals, and the
high-voltage motive devices and the power supply circuit thereof cannot
be protected in real time. Thus, a protection circuit that can protect
high-voltage motive devices (for example, solenoids or electronic
clutches) when a failure occurs is to be provided such that the
high-voltage motive devices can be prevented from being burnt and the
fabrication cost of the MFP can be reduced.

SUMMARY OF THE INVENTION

[0007]The present invention provides an over-current protection device for
multiple high-voltage motive devices. The over-current protection device
includes a comparison module and a logic operation module. The comparison
module receives a plurality of voltages generated from a plurality of
operating currents of a plurality of high-voltage motive devices and
respectively compares the voltages with at least one reference voltage to
generate a plurality of comparison results, wherein the high-voltage
motive devices are a plurality of solenoids, a plurality of electronic
clutches, or a combination of solenoids and electronic clutches. The
logic operation module receives the comparison results and generates at
least one control signal for a plurality of high-voltage motive device
driving circuits according to the comparison results. The high-voltage
motive device driving circuits respectively drive the high-voltage motive
devices according to the control signal.

[0008]According to an embodiment of the present invention, the
over-current protection device further includes a main power control
module. The logic operation module further generates a main power control
signal for the main power control module according to the comparison
results. The main power control module generates a main power off control
signal for a main power circuit according to the main power control
signal so that the main power circuit turns off a multiple high-voltage
motive device voltage source supplied by the main power circuit according
to the main power off control signal.

[0009]According to an embodiment of the present invention, the
over-current protection device includes an integrator and a comparator.
The integrator receives the main power control signal and generates an
integrated voltage. The comparator receives a predetermined voltage and
the integrated voltage and compares the integrated voltage with the
predetermined voltage to generate the main power off control signal.

[0010]According to an embodiment of the present invention, when the
voltage generated from the operating current of one of the high-voltage
motive devices is greater than the reference voltage, the logic operation
module outputs the control signal to turn off one, all, or a part of the
high-voltage motive devices, or the main power control module turns off
the high-voltage motive device voltage source supplied by the main power
circuit.

[0011]The present invention provides an over-current protection method for
multiple high-voltage motive devices. First, a plurality of voltages
generated from a plurality of operating currents of a plurality of
high-voltage motive devices is received, wherein the high-voltage motive
devices are a plurality of solenoids, a plurality of electronic clutches,
or a combination of solenoids and electronic clutches. Then, the voltages
are respectively compared with at least one reference voltage to generate
a plurality of comparison results. Next, at least one logic operation is
performed on the comparison results to generate at least one control
signal for a plurality of high-voltage motive device driving circuits.
After that, the high-voltage motive devices are respectively driven by
the high-voltage motive device driving circuits according to the control
signal.

[0012]According to an embodiment of the present invention, the
over-current protection method further includes following steps. The
logic operation is performed on the comparison results to generate a main
power control signal for a main power control module. Then, a main power
off control signal is generated by the main power control module for a
main power circuit according to the main power control signal, so that
the main power circuit turns off a high-voltage motive device voltage
source supplied by the main power circuit according to the main power off
control signal.

[0013]According to an embodiment of the present invention, the step of
generating the main power off control signal further includes following
steps. First, the main power control signal is integrated to generate an
integrated voltage. Then, the integrated voltage is compared with the
predetermined voltage to generate the main power off control signal.

[0014]As described above, the present invention provides an over-current
protection device for multiple high-voltage motive devices and a method
thereof, wherein when at least one of a plurality of high-voltage motive
devices fails, driving circuits of the high-voltage motive devices and
the main power circuit are automatically turned off, or some of the
driving circuits and the main power circuit are sequentially turned off
so that a multifunction printer (MFP) can be protected in real time.
Thereby, sheet metals on the high-voltage motive devices can be removed
and accordingly the fabrication cost of the MFP can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]The accompanying drawings are included to provide a further
understanding of the invention, and are incorporated in and constitute a
part of this specification. The drawings illustrate embodiments of the
invention and, together with the description, serve to explain the
principles of the invention.

[0016]FIG. 1 is a diagram of an over-current protection device for
multiple high-voltage motive devices according to an embodiment of the
present invention.

[0017]FIG. 2 is a diagram of a comparison module according to an
embodiment of the present invention.

[0018]FIG. 3 is a diagram of a logic operation module according to an
embodiment of the present invention.

[0020]FIG. 4D is a diagram of a solenoid voltage supply module according
to an embodiment of the present invention.

[0021]FIG. 5 is a diagram of a main power circuit according to an
embodiment of the present invention.

[0022]FIG. 6 is a diagram of an over-current protection device for
multiple high-voltage motive devices according to another embodiment of
the present invention.

[0023]FIG. 7 is a flowchart of an over-current protection method for
multiple high-voltage motive devices according to an embodiment of the
present invention.

DESCRIPTION OF THE EMBODIMENTS

[0024]Reference will now be made in detail to the present preferred
embodiments of the invention, examples of which are illustrated in the
accompanying drawings. Wherever possible, the same reference numbers are
used in the drawings and the description to refer to the same or like
parts.

[0025]In an embodiment of the present invention, an over-current
protection device for multiple high-voltage motive devices is provided.
When a multifunction printer (MFP) fails, the over-current protection
device can carry out over-current protection on high-voltage motive
devices, such as solenoids or electronic clutches.

[0026]FIG. 1 is a diagram of an over-current protection device for
multiple high-voltage motive devices according to an embodiment of the
present invention. Referring to FIG. 1, the over-current protection
device 1 includes a comparison module 14 and a logic operation module 15.
In the present embodiment, the high-voltage motive devices are described
as solenoids S1-S3. However, the over-current protection device 1
provided by the present invention is not only applied to the solenoids
S1-S3 and may also be applied to electronic clutches. In addition, even
though FIG. 1 illustrates the solenoids S1-S3, the number of the
solenoids is not limited in the present invention.

[0027]The solenoids S1-S3 are respectively driven by solenoid driving
circuits 11-13. The solenoid driving circuits 11-13 receive a solenoid
voltage VSOLENOID that is higher than the supply voltages of other
elements and respectively determine whether to supply driving voltages or
driving currents to the solenoids S1-S3 according to control signals
CTR1-CTR3. The solenoid current detection circuits DET1-DET3 are
respectively connected to the solenoids S1-S3, and which detect the
operating currents I1-I3 of the solenoids S1-S3 and respectively generate
voltages V1-V3 according to the operating currents I1-I3. In the present
embodiment, the solenoid current detection circuits DET1-DET3 are
respectively composed of resistors R1-R3. However, the implementation of
the solenoid current detection circuits DET1-DET3 is not limited in the
present invention.

[0028]The comparison module 14 receives the voltages V1-V3 generated from
the operating currents I1-I3 of the solenoids S1-S3 and respectively
compares the voltages V1-V3 with reference voltages VREF1-VREF3 to
generate comparison results COM_OUT1-COM_OUT3. In the present embodiment,
the solenoid current detection circuits DET1-DET3 and the comparison
module 14 are separately designed. However, in an actual application, the
comparison module 14 may include the solenoid current detection circuits
DET1-DET3.

[0029]In addition, the comparison module 14 includes a plurality of
comparators COM1-COM3, wherein the comparators COM1-COM3 are implemented
with operational amplifiers. The comparator COM1 compares the voltage V1
received from the negative input terminal thereof with the reference
voltage VREF1 received from the positive input terminal thereof to output
the comparison result COM_OUT1. The comparator COM2 compares the voltage
V2 received from the negative input terminal thereof with the reference
voltage VREF2 received from the positive input terminal thereof to output
the comparison result COM_OUT2. The comparator COM3 compares the voltage
V3 received from the negative input terminal thereof with the reference
voltage VREF3 received from the positive input terminal thereof to output
the comparison result COM_OUT3. It should be noted that the
implementation of the comparison module 14 is not limited to that
illustrated in FIG. 1.

[0030]Additionally, the reference voltages VREF1-VREF3 may be generated by
the reference voltage generators VDIV1-VDIV3. The reference voltage
generator VDIV1 includes resistors R4 and R5 that are connected in
series. The reference voltage generator VDIV1 receives a system voltage
VCC and generates the reference voltage VREF1 according to the ratio
between the resistors R4 and R5. Similarly, the reference voltage
generator VDIV2 generates the reference voltage VREF2 according to the
ratio between the resistors R6 and R7, and the reference voltage
generator VDIV3 generates the reference voltage VREF3 according to the
ratio between the resistors R8 and R9. The resistances of the resistors
R4-R9 can be determined according to the current limits of the solenoids
S1-S3. In other words, different reference voltages VREF1-VREF3 are
generated according to the current limits of the solenoids S1-S3. In the
present embodiment, the reference voltage generators VDIV1-VDIV3 are
implemented outside of the comparison module 14. However, in an actual
application, the reference voltage generators VDIV1-VDIV3 may also be
implemented in the comparison module 14.

[0031]Next, the logic operation module 15 receives the comparison results
COM_OUT1-COM_OUT3 and performs at least one logic operation according to
the comparison results COM_OUT1-COM_OUT3 to generate a plurality of
control signals CTR1-CTR3 for the solenoid driving circuits 11-13. The
control signals CTR1-CTR3 may be the same control signal or different
control signals. The logic operations performed for generating the
control signals CTR1-CTR3 may be the same logic operation or different
logic operations.

[0032]In the present embodiment, the over-current protection device 1
further includes a main power control module 18, and the logic operation
module 15 generates a main power control signal Y2 for the main power
control module 18 according to the comparison results COM_OUT1-COMOUT3.
The main power control module 18 generates a main power off control
signal COM_OUT4 for a main power circuit 19 according to the main power
control signal Y2, so as to control the main power circuit 19 to stop
supplying the solenoid voltage VSOLENOID (an electronic clutch voltage
VCLUTCH if the high-voltage motive devices are electronic clutches) and a
motor voltage VMOTOR.

[0033]In FIG. 1, the over-current protection device 1 may further include
a processor 16. The processor 16 receives a power-off indication signal
Y2 (in another embodiment, the processor 16 may also receive a power-off
indication signal Y1), wherein the power-off indication signal Y2
indicates which solenoids fail. Besides, the processor 16 generates
prompt signals ENS1-ENS3 according to the power-off indication signal Y2.
The logic operation module 15 generates the control signals CTR1-CTR3
according to the prompt signals ENS1-ENS3 and the power-off indication
signal Y2.

[0034]The over-current protection device 1 may further include a display
module 17. The processor 16 generates a warning signal for the display
module 17 according to the power-off indication signal Y2. The display
module 17 displays error states of the solenoids S1-S3 according to the
warning signal. Accordingly, a user or a maintenance guy can eliminate
the problem according to the error states of the solenoids S1-S3
displayed by the display module 17.

[0035]In the present embodiment, the logic operation module 15 includes a
plurality of logic AND gates AND1-AND5. The logic AND gate AND1 performs
a logic AND operation on the comparison results COM_OUT1 and COM_OUT2 to
output the power-off indication signal Y1. The logic AND gate AND2
performs a logic AND operation on the comparison result COM_OUT3 and the
power-off indication signal Y1 to output the power-off indication signal
Y2, wherein the power-off indication signal Y2 is also the main power
control signal Y2 output to the main power control module 18. The logic
AND gate AND3 performs a logic AND operation on the prompt signal ENS1
and the power-off indication signal Y2 to output the control signal CTR1.
The logic AND gate AND4 performs a logic AND operation on the prompt
signal ENS2 and the power-off indication signal Y2 to output the control
signal CTR2. The logic AND gate ANDS performs a logic AND operation on
the prompt signal ENS3 and the power-off indication signal Y2 to output
the control signal CTR3.

[0036]No extra operating currents I1-I3 will be produced when the
solenoids S1-S3 operate normally. In this case, the comparison results
COM_OUT1-COM_OUT3 are logic high level signals and the power-off
indication signal Y2, the control signals CTR1-CTR3, the prompt signals
ENS1-ENS3, and the main power off control signal COM_OUT4 are all logic
high level signals. Thus, the solenoid driving circuits 11-13
respectively drive the solenoids S1-S3.

[0037]However, when one of the solenoids (for example, the solenoid S1)
fails, the comparison result COM_OUT1 becomes a logic low level signal,
and the power-off indication signal Y2, the control signals CTR1-CTR3,
the prompt signals ENS1-ENS3, and the main power off control signal
COM_OUT4 all become logic low level signals.

[0038]Thus, the solenoid driving circuits 11-13 are disabled and cannot
drive the solenoids S1-S3. Meanwhile, the main power circuit 19 is also
disabled and stops supplying the motor voltage VMOTOR and the solenoid
voltage VSOLENOID.

[0039]In the present embodiment, the solenoid driving circuits 11-13 and
the main power circuit 19 are all turned off if one solenoid fails.
However, it should be noted that the present invention is not limited
thereto. In another embodiment, the logic operation module 15 may also be
implemented by using a plurality of different logic gates so that all or
some of the solenoid driving circuits 11-13 are disabled first to protect
the corresponding ones of the solenoids S1-S3 and the main power circuit
19 is turned off after that. In short, the logic operation module 15 can
be designed according to the order in which the elements are intended to
be protected.

[0040]The main power control module 18 includes an integrator VINT and a
comparator COM4. The integrator VINT receives the main power control
signal Y2 and generates an integrated voltage V4. The integrator VINT may
be implemented by using a resistor R10 and a capacitor C1. However, the
implementation of the integrator VINT is not limited in the present
invention, and the integrator VINT may also be implemented differently.
The comparator COM4 compares a predetermined voltage VPRESET received by
the positive input terminal thereof and the integrated voltage V4
received by the negative input terminal thereof to generate the main
power off control signal COMOUT4. The predetermined voltage VPRESET may
be generated by a reference voltage generator VDIV4. The reference
voltage generator VDIV4 includes two resistors R11 and R12 that are
connected in series. As described above, the implementation of the
reference voltage generator VDIV4 is not limited in the present
invention. In addition, the comparator COM4 may also be implemented in
the comparison module 14 instead of as a separate comparator.

[0041]FIG. 2 is a diagram of a comparison module according to an
embodiment of the present invention. Referring to FIG. 2, the comparison
module 14 can be implemented by using two existing comparator chips 21
and 22 in the market. In the present embodiment, the comparator COM4 in
FIG. 1 is also implemented in the comparison module 14 to reduce the
surface area and the fabrication cost of the chip. The comparator chip 21
or 22 includes two comparators and has 8 pins, wherein the 8 pins are
respectively defined as an output terminal OUT1 of the first comparator,
a negative input terminal -IN1 of the first comparator, a positive input
terminal +IN1 of the first comparator, a ground terminal VEE, a positive
input terminal +IN2 of the second comparator, a negative input terminal
-IN2 of the second comparator, an output terminal OUT2 of the second
comparator, and a system voltage VCC.

[0042]The 8 pins of the comparator chip 21 are respectively connected to
the comparison result COM_OUT1, the voltage V1, the reference voltage
VREF1, the ground, the predetermined voltage VPRESET, the voltage V4, the
main power off control signal COM_OUT4, and a 5V voltage. The 8 pins of
the comparator chip 22 are respectively connected to the comparison
result COM_OUT3, the voltage V3, the reference voltage VREF3, the ground,
the reference voltage VREF2, the voltage V2, the comparison result
COM_OUT2, and the 5V voltage. Herein the comparator COM4 and the
comparator COM1 of the main power control module 18 are implemented in
the same comparator chip 21 so that no other comparator chip is required.

[0043]FIG. 3 is a diagram of a logic operation module according to an
embodiment of the present invention. Referring to FIG. 3, the logic
operation module 15 in FIG. 1 can be implemented by using two existing
logic AND gate chips 31 and 32 in the markets. The logic AND gate chip 31
or 32 has 4 logic AND gates and 14 pins, wherein the 14 pins are
respectively defined as an input terminal 1A of the first logic AND gate,
an input terminal 1B of the first logic AND gate, an output terminal 1Y
of the first logic AND gate, an input terminal 2A of the second logic AND
gate, an input terminal 2B of the second logic AND gate, an output
terminal 2Y of the second logic AND gate, a ground terminal GND, an
output terminal 3Y of the third logic AND gate, an input terminal 3A of
the third logic AND gate, an input terminal 3B of the third logic AND
gate, an output terminal 4Y of the fourth logic AND gate, an input
terminal 4A of the fourth logic AND gate, an input terminal 4b of the
fourth logic AND gate, and the system voltage VCC.

[0044]The 14 pins of the logic AND gate chip 31 are respectively connected
to the comparison result COM_OUT1, the comparison result COM_OUT2, the
power-off indication signal Y1, the power-off indication signal Y1, the
comparison result COM_OUT3, the power-off indication signal Y2, the
ground, the control signal CTR1, the power-off indication signal Y2, the
prompt signal ENS1, the control signal CTR2, the power-off indication
signal Y2, the prompt signal ENS2, and the 5V voltage. The
1st-6th and 11th-13th pins of the logic AND gate chip
32 are respectively floated and not in use, and the 7th-10th
pins and the 14th pin thereof are respectively connected to the
ground, the control signal CTR3, the power-off indication signal Y2, the
prompt signal ENS3, and the 5V voltage.

[0045]FIGS. 4A-4C are respectively partial circuit diagrams of solenoid
driving circuits in FIG. 1. Referring to FIGS. 4A-4C, the solenoid
driving circuit 11 includes a transistor Q1 and resistors R13 and R14.
Similarly, the solenoid driving circuit 12 includes a transistor Q2 and
resistors R15 and R16, and the solenoid driving circuit 13 includes a
transistor Q3 and resistors R17 and R18. The transistors Q1-Q3 are
bipolar junction transistors (BJTs). The drains of the transistors Q1-Q3
respectively receive the voltages P1-P3 generated according to the
solenoid voltage VSOLENOID, and the gates thereof respectively receive
the control signals CTR1-CTR3. When the control signals CTR1-CTR3 are
logic low level signals, the transistors Q1-Q3 are turned off so that no
extra operating currents I1-I3 is produced. FIG. 4D is a diagram of a
solenoid voltage supply module according to an embodiment of the present
invention. Referring to FIG. 4D, the voltages P1-P3 in FIGS. 4A-4C can be
generated by the solenoid voltage supply module 41. The solenoid voltage
supply module 41 is an existing power connector in the market, and which
receives the solenoid voltage VSOLENOID and generates the voltages P1-P3.

[0046]FIG. 5 is a diagram of a main power circuit according to an
embodiment of the present invention. Referring to FIG. 5, the main power
circuit 19 includes transistors M1 and M2, resistors R19 and R20, and a
capacitor C2. The transistor M1 is an N-type depletion
metal-oxide-semiconductor field-effect transistor (MOSFET), and the
transistor M2 is a P-type enhanced MOSFET. When the main power off
control signal COM_OUT4 received by the gate of the transistor M1 is a
logic low level signal, the transistor M1 and the transistor M2 are
turned off. Accordingly, the main power circuit 19 stops supplying the
motor voltage VMOTOR and the solenoid voltage VSOLENOID.

[0047]FIG. 6 is a diagram of an over-current protection device for
multiple high-voltage motive devices according to another embodiment of
the present invention. Referring to FIG. 6, the difference between the
over-current protection device 6 and the over-current protection device 1
illustrated in FIG. 1 is that the logic operation module 65 is
implemented by using a plurality of logic NOR gates NOR1-NOR5 and a NOT
gate INV1. Thus, the control signals CTR1-CTR3 used for disabling the
solenoid driving circuits 11-13 and the main power off control signal
COM_OUT4 used for disabling the main power circuit 19 are logic high
level signals. The corresponding elements can be disabled since the
control signals CTR1-CTR3 and the main power off control signal COM_OUT4
are logic high level signals. Thus, the positive input terminals and the
negative input terminals of the comparators COM1-COM4 in FIG. 4 are
reverse to the positive input terminals and the negative input terminals
of the comparators COM1-COM4 in FIG. 1. For example, the positive input
terminal and the negative input terminal of the comparator COM1 in FIG. 4
respectively receive the voltage V1 and the reference voltage VREF1.
However, the positive input terminal and the negative input terminal of
the comparator COM1 in FIG. 1 respectively receive the reference voltage
VREF1 and the voltage V1.

[0048]FIG. 7 is a flowchart of an over-current protection method for
multiple high-voltage motive devices according to an embodiment of the
present invention. Referring to FIG. 7, in step S71, the operating
currents of the high-voltage motive devices are detected. Then, in step
S72, the voltages generated from the operating currents of the
high-voltage motive devices are compared with the reference voltages to
generate the comparison results. Next, in step S73, at least one a logic
operation is performed on the comparison results to generate at least one
control signal. Finally, in step S74, the high-voltage motive devices are
driven according to the control signal.

[0049]In summary, the present invention provides an over-current
protection device for multiple high-voltage motive devices and a method
thereof, wherein when at least one of a plurality of high-voltage motive
devices fails, driving circuits of the high-voltage motive devices and
the main power circuit are automatically turned off, or some of the
driving circuits and the main power circuit are sequentially turned off
so that a MFP can be protected in real time. Thereby, sheet metals on the
high-voltage motive devices can be removed and accordingly the
fabrication cost of the MFP can be reduced.

[0050]It will be apparent to those skilled in the art that various
modifications and variations can be made to the structure of the present
invention without departing from the scope or spirit of the invention. In
view of the foregoing, it is intended that the present invention cover
modifications and variations of this invention provided they fall within
the scope of the following claims and their equivalents.